Cellulose composite membrane based on phase separation-crosslinking modification as well as preparation method and application of cellulose composite membrane

Abstract

The invention relates to the technical field of modified cellulose membranes, in particular to a cellulose composite membrane based on phase separation-cross-linking modification as well as a preparation method and application thereof, and particularly provides a method for preparing a cellulose composite membrane based on phase separation-cross-linking modification on a polyacrylonitrile (PAN) supporting layer by taking novel ionic liquid (AMIMCL) as a solvent for dissolving cellulose, water as a non-solvent and glutaraldehyde (GA) as a cross-linking agent. The novel cross-linked compact cellulose pervaporation membrane is prepared through a phase separation method and is applied to separation of a mixed system of ethyl acetate / water and acetic acid / water, the acid resistance and separation stability of a membrane material are improved, and a theoretical basis is provided for optimization of pervaporation dehydration performance.

Description

Technical field

[0001] The present invention belongs to the technical field of modified cellulose membranes, and in particular relates to a cellulose composite membrane based on phase separation-crosslinking modification, and a preparation method and application thereof. [Background Technology]

[0002] The development of an acid-resistant pervaporation membrane using cellulose as a raw material for the dehydration and separation of mixed liquors in acetic acid esterification systems not only facilitates the functional utilization of biomass resources but also enables green enhancement of the esterification production process, achieving energy conservation, consumption reduction, and improved economic benefits. The non-solvent-induced phase separation method, which introduces a non-solvent into a homogeneous polymer solution, induces phase separation to form polymer-poor and polymer-rich phases. By varying the phase separation conditions, the structure and properties of the membrane material can be manipulated. This method, characterized by its ease of operation, high efficiency, and controllability, is widely used in the preparation of polymer membrane materials.

[0003] However, cellulose (Cel), as a biomacromolecule, contains numerous hydrogen bonds both intramolecularly and intramolecularly, making it difficult for conventional solvents to dissolve it, thus failing to meet membrane-forming requirements. Consequently, this material is relatively rarely used in pervaporation separations. Traditional cellulose dissolution processes, such as the viscose and cuprammonia methods, utilize highly toxic substances, causing environmental pollution and harming human health. These methods also consume high amounts of energy, necessitating the development of green solvents that can effectively dissolve cellulose.

[0004] Compared with traditional organic solvents, ionic liquids offer advantages such as environmental friendliness, strong solubility, and adjustable structure. Selecting the right ionic liquid solvent as a cellulose solvent is crucial for the development of fiber membranes. Furthermore, cellulose membranes in acetic acid / water systems suffer from low separation selectivity, poor acid resistance, and poor cyclic stability. Because the esterification system contains acidic and strong solvent chemicals such as acetic acid and ethyl acetate, the glycosidic bonds in the cellulose macromolecules are easily broken and hydrolyzed in an acidic environment, resulting in poor stability of the cellulose membrane material. This poses challenges to the mechanical strength, acid resistance, and stability of the cellulose membrane material. [Summary of the invention]

[0005] In view of the above, it is necessary to provide a cellulose composite membrane based on phase separation-crosslinking modification, and its preparation method and application. It uses a new ionic liquid as a solvent for dissolving cellulose, water as a non-solvent, and glutaraldehyde as a cross-linking agent. A new cross-linked dense cellulose pervaporation membrane is prepared by a phase separation method on a polyacrylonitrile support layer, and is used for the separation of ethyl acetate / water and acetic acid / water mixed systems, thereby improving the acid resistance and separation stability of the membrane material.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing a cellulose composite membrane based on phase separation-crosslinking modification, the method comprising the following steps:

[0008] (1) dissolving cellulose in an ionic liquid and stirring the solution under heating conditions in a water bath to prepare a homogeneous membrane casting solution;

[0009] (2) Add glutaraldehyde to the homogeneous casting solution and continue heating for 25-35 minutes;

[0010] (3) Soaking the PAN nanofiber support layer in a NaOH solution on a hot plate for 25-35 min, then taking it out and repeatedly washing it with deionized water several times to remove residual NaOH to obtain a treated PAN support layer;

[0011] (4) After the PAN support layer treated in step (3) is dried, it is spread flat on a smooth glass plate and fixed on a heating plate. The temperature is controlled to be 85-95°C. The casting liquid obtained in step (2) is poured along the edge of the PAN support layer. The distance between the scraper and the glass plate is controlled to be 220-280 μm. The film is scraped from bottom to top. Then, the glass plate is immersed in deionized water; after soaking, it is taken out and drained, and then dried to obtain the cellulose composite membrane.

[0012] In the present invention, further, in the step (1), the ionic liquid is AMIMCL, the water bath heating temperature is 90° C., the stirring time is 4 h, and the cellulose mass fraction of the prepared homogeneous casting solution is 6%.

[0013] In the present invention, further, the mass fraction of glutaraldehyde in step (2) is 0.1-0.4 wt%.

[0014] In the present invention, further, in step (3), the temperature of the heating plate is 65° C., and the concentration of the NaOH solution is 2 mol / L.

[0015] In the present invention, further, the drying in step (4) is specifically: placing the PAN support layer in a vacuum oven and drying it at 90° C. for 1 hour.

[0016] In the present invention, further, in step (4), the glass plate is immersed in deionized water at room temperature for 24 hours.

[0017] In the present invention, further, the drying treatment in step (4) is specifically to place the product in a vacuum oven at 90° C. and dry it for 1 hour.

[0018] The present invention also provides a cellulose composite membrane based on phase separation-crosslinking modification, and the cellulose composite membrane based on phase separation-crosslinking modification is prepared by the method described above.

[0019] The present invention also provides an application of a cellulose composite membrane based on phase separation-crosslinking modification, wherein the cellulose composite membrane is used for separating a mixed system of ethyl acetate / water and acetic acid / water.

[0020] The present invention has the following beneficial effects:

[0021] The present invention proposes a cellulose composite membrane based on phase separation and cross-linking modification and its preparation method. This method uses a novel ionic liquid as a cellulose dissolving solvent, water as a non-solvent, and glutaraldehyde as a cross-linking agent. A novel cross-linked, dense cellulose pervaporation membrane is prepared on a polyacrylonitrile support layer via a phase separation method. The composite membrane is then applied to the separation of ethyl acetate / water and acetic acid / water mixed systems. Compared to uncross-linked membranes, the present method improves acetic acid / water separation selectivity by 30% to 50%, reduces acid swelling resistance by more than 40%, and maintains mechanical strength >90% after 10 cycles. The present invention features a simple process, low material cost, and requires only a single cross-linking reaction. It effectively achieves synergistic optimization of membrane structural stability and separation performance, providing a theoretical basis for optimizing pervaporation dehydration performance and making it suitable for industrial scale-up production.

Brief Description of the Drawings

[0022] Figure 1 is the SEM image of GA-Cel / PAN membrane;

[0023] Figure 2 is the effect of GA content on the water contact angle of GA-Cel / PAN;

[0024] Figure 3 is the thermogravimetric analysis of Cel(1) and Cel(4);

[0025] Figure 4 is the FTIR spectra of GA-Cel / PAN films with different cross-linking degrees;

[0026] Figure 5 is the XRD spectra of GA-Cel / PAN films with different cross-linking degrees;

[0027] Figure 6 is the mechanical strength of GA-Cel / PAN with different cross-linking degrees;

[0028] Figure 7 This is the swelling test result of GA-Cel / PAN membrane material;

[0029] Figure 8 The effect of GA content on the pervaporation separation performance of GA-Cel / PAN membrane;

[0030] Figure 9 This is the stability test result of GA-Cel / PAN membrane. [Specific implementation method]

[0031] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0032] Example 1:

[0033] This embodiment proposes a method for preparing a cellulose composite membrane based on phase separation-crosslinking modification, and the steps are as follows:

[0034] (1) Cellulose was dissolved in the ionic liquid AMIMCL, heated in a water bath at 90°C and stirred for 4 h to prepare a homogeneous casting solution with a cellulose mass fraction of 6%;

[0035] (2) Add 0.1 wt% glutaraldehyde to the homogeneous casting solution and continue heating for 25 min;

[0036] (3) Soaking the PAN nanofiber support layer in a 2 mol / L NaOH solution on a 65°C hot plate for 25 min, then taking it out and repeatedly washing it with deionized water to remove residual NaOH to obtain a treated PAN support layer;

[0037] (4) The PAN support layer treated in step (3) is placed in a vacuum oven and dried at 90°C for 1 hour. Then, it is spread flat on a smooth glass plate and fixed on a heating plate. The temperature is controlled at 85°C. The casting liquid obtained in step (2) is poured along the edge of the PAN support layer. The distance between the scraper and the glass plate is controlled to be 220 μm. The film is scraped from bottom to top. Then, the glass plate is placed in deionized water and soaked at room temperature for 24 hours. After soaking, it is taken out and drained, and placed in a vacuum oven at 90°C for 1 hour to obtain the cellulose composite membrane.

[0038] Example 2:

[0039] This embodiment proposes a method for preparing a cellulose composite membrane based on phase separation-crosslinking modification, and the steps are as follows:

[0040] (1) Cellulose was dissolved in the ionic liquid AMIMCL, heated in a water bath at 90°C and stirred for 4 h to prepare a homogeneous casting solution with a cellulose mass fraction of 6%;

[0041] (2) Add 0.2 wt% glutaraldehyde to the homogeneous casting solution and continue heating for 30 min;

[0042] (3) Soaking the PAN nanofiber support layer in a 2 mol / L NaOH solution on a 65°C hot plate for 30 min, then taking it out and repeatedly washing it with deionized water to remove residual NaOH to obtain a treated PAN support layer;

[0043] (4) The PAN support layer treated in step (3) is placed in a vacuum oven and dried at 90°C for 1 hour. Then, it is spread flat on a smooth glass plate and fixed on a heating plate. The temperature is controlled to be 88°C. The casting liquid obtained in step (2) is poured along the edge of the PAN support layer. The distance between the scraper and the glass plate is controlled to be 250 μm. The film is scraped from bottom to top. Then, the glass plate is placed in deionized water and soaked at room temperature for 24 hours. After soaking, it is taken out and drained, and placed in a vacuum oven at 90°C for 1 hour to obtain the cellulose composite membrane.

[0044] Example 3:

[0045] This embodiment proposes a method for preparing a cellulose composite membrane based on phase separation-crosslinking modification, and the steps are as follows:

[0046] (1) Cellulose was dissolved in the ionic liquid AMIMCL, heated in a water bath at 90°C and stirred for 4 h to prepare a homogeneous casting solution with a cellulose mass fraction of 6%;

[0047] (2) Add 0.3 wt% glutaraldehyde to the homogeneous casting solution and continue heating for 32 min;

[0048] (3) Soaking the PAN nanofiber support layer in a 2 mol / L NaOH solution on a 65°C hot plate for 32 min, then taking it out and repeatedly washing it with deionized water to remove residual NaOH to obtain a treated PAN support layer;

[0049] (4) The PAN support layer treated in step (3) is placed in a vacuum oven and dried at 90°C for 1 hour. Then, it is spread flat on a smooth glass plate and fixed on a heating plate. The temperature is controlled at 88°C. The casting liquid obtained in step (2) is poured along the edge of the PAN support layer. The distance between the scraper and the glass plate is controlled to be 260 μm. The film is scraped from bottom to top. Then, the glass plate is placed in deionized water and soaked at room temperature for 24 hours. After soaking, it is taken out and drained, and placed in a vacuum oven at 90°C for 1 hour to obtain the cellulose composite membrane.

[0050] Example 4:

[0051] This embodiment proposes a method for preparing a cellulose composite membrane based on phase separation-crosslinking modification, and the steps are as follows:

[0052] (1) Cellulose was dissolved in the ionic liquid AMIMCL, heated in a water bath at 90°C and stirred for 4 h to prepare a homogeneous casting solution with a cellulose mass fraction of 6%;

[0053] (2) Add 0.4 wt% glutaraldehyde to the homogeneous casting solution and continue heating for 35 min;

[0054] (3) Soaking the PAN nanofiber support layer in a 2 mol / L NaOH solution on a 65°C hot plate for 35 min, then taking it out and repeatedly washing it with deionized water to remove residual NaOH to obtain a treated PAN support layer;

[0055] (4) The PAN support layer treated in step (3) is placed in a vacuum oven and dried at 90°C for 1 hour. Then, it is spread flat on a smooth glass plate and fixed on a heating plate. The temperature is controlled at 95°C. The casting liquid obtained in step (2) is poured along the edge of the PAN support layer. The distance between the scraper and the glass plate is controlled to be 280 μm. The film is scraped from bottom to top. Then, the glass plate is placed in deionized water and soaked at room temperature for 24 hours. After soaking, it is taken out and drained, and placed in a vacuum oven at 90°C for 1 hour to obtain the cellulose composite membrane.

[0056] Test example:

[0057] To demonstrate the practical value of this application, the applicants used SEM to observe the evolution of the membrane surface and cross-section micromorphology before and after cross-linking. FTIR and XRD were used to analyze the intermolecular cross-linking reaction mechanism and the changes in the crystalline structure. WCA was used to quantitatively characterize the effect of regulating the hydrophilicity / hydrophobicity of the membrane surface. Mechanical strength tests were performed to evaluate the enhancement of the mechanical properties of the material by cross-linking. Equilibrium swelling experiments were used to investigate the inhibitory effect of the cross-linking degree on the swelling behavior of the membrane material in ethyl acetate / water and acetic acid / water systems. This systematic exploration of the regulatory mechanism of glutaraldehyde cross-linking on the physical and chemical properties of Cel / PAN membranes provides a theoretical basis for optimizing pervaporation dehydration performance.

[0058] The specific tests are as follows:

[0059] Membrane material appearance characterization and analysis:

[0060] The surface and cross-sectional SEM images of GA-Cel / PAN membrane materials with glutaraldehyde mass fractions of 0.1 to 0.4 wt% are shown in Figure 2. Figure 1 As shown, Figure 1 (a~d) are surface SEM images of GA-Cel / PAN membrane materials. Figure 1(e-h) are cross-sectional SEM images of the GA-Cel / PAN membrane. The results show that the surface roughness of the cellulose membrane increases after cross-linking. Furthermore, as the degree of cross-linking increases, the bond between the separation layer and the support layer becomes tighter and more uniform, resulting in a dense membrane structure with no apparent pores.

[0061] The contact angles of GA-Cel / PAN membrane materials with glutaraldehyde mass fractions of 0.1 to 0.4 wt% are as follows: Figure 2 As shown, Figure 2 It can be seen from the figure that when the contact angle of Cel / PAN membrane material increases from 0.1wt% to 0.4wt%, the contact angle of the membrane material surface decreases from 59° to 49°, which indicates that glutaraldehyde cross-linking improves the surface hydrophilicity of the membrane material. Therefore, cross-linking is beneficial to the adsorption of water molecules on the surface of the membrane material, thereby enhancing the adsorption selectivity of the membrane material and improving the separation performance.

[0062] Thermogravimetric (TGA) analysis:

[0063] Figure 3 The thermal decomposition behavior of cellulose membrane materials with different glutaraldehyde crosslinker contents is shown. As can be seen from the figure, as the temperature increases, the weight loss of all samples gradually increases, but the weight loss of Cel-6 (4) with a crosslinker content of 4% at 600-700℃ is significantly lower than that of Cel-6 (1) with a crosslinker content of 1%. In addition, the DTG value tends to decrease with the increase of crosslinker content. This shows that the glutaraldehyde crosslinker enhances the thermal stability of cellulose by forming an intermolecular crosslinking network. The higher crosslinking density in Cel-6 (4) limits the thermal motion of the molecular chain and delays the release of volatile products during thermal decomposition, thereby showing lower weight loss and slower decomposition rate at high temperature. Cel-6 (1) has a lower degree of crosslinking, and its molecular chain is more easily broken, resulting in earlier thermal decomposition and faster rate. This shows that the high temperature resistance of cellulose materials can be optimized by regulating the crosslinker ratio.

[0064] FTIR analysis:

[0065] Figure 4 The infrared spectra of GA-Cel / PAN films with different crosslinker contents are shown in Figure 2. When the glutaraldehyde crosslinker content increases from 0 wt% to 0.4 wt%, the 3600-3200 cm -1 The hydroxyl (OH) stretching vibration peak intensity at 1700 cm-1 shows a decreasing trend, which indicates that the hydroxyl groups on the cellulose molecular chain are gradually consumed during the cross-linking reaction. It is worth noting that although the glutaraldehyde molecule contains carbonyl functional groups, the hydroxyl group at 1700 cm-1 is not significantly different from the glutaraldehyde molecule. - No obvious C=O characteristic absorption peak was detected near 1, which indicates that glutaraldehyde was completely consumed during the cross-linking process. -A significant enhancement and broadening of the COC asymmetric stretching vibration peak were observed within the range of 1, indicating that a stable covalent cross-linking network was formed between glutaraldehyde and cellulose molecules through hemiacetal bonding, which is beneficial to increasing the structural stability and acid resistance of the membrane material.

[0066] XRD analysis:

[0067] Crystal structure analysis based on XRD spectra shows that the crosslinking agent content has a certain influence on the microcrystalline structure of regenerated cellulose membrane. Figure 5 As shown in the figure, the Cel-6 film without the addition of crosslinking agent exhibits typical diffraction peaks of cellulose II crystal form at 2θ = 14.8°, 16.4° and 22.5°, corresponding to the (110), (110) and (020) crystal planes, respectively. As the crosslinking agent dosage increases from 0.1wt% to 0.4wt%, the intensity of the cellulose characteristic diffraction peak of the typical cellulose II crystal form gradually increases, and the peak shape tends to be sharper. This indicates that the crosslinking agent restricts the free movement of cellulose chain segments through intermolecular crosslinking. The steric hindrance effect generated by the crosslinking network reduces the free volume fraction of the cellulose amorphous region, thereby enhancing the crystalline structure.

[0068] Mechanical strength analysis:

[0069] like Figure 6 As shown, as the glutaraldehyde (GA) mass fraction increases from 0.0wt% to 0.3wt%, the tensile strength of the GA-Cel / PAN film shows a significant improvement, increasing from an initial 51.5 MPa to a maximum of 60.6 MPa, while maintaining a strain at break of 21.5%. This strengthening effect can be attributed to the formation of an intermolecular covalent network through moderate crosslinking, which effectively enhances the interactions between polymer chains and optimizes the material's rigidity. However, when the GA content continues to increase to 0.4wt%, the tensile strength decreases to 54.8 MPa, and the strain at break also decreases significantly to 17.6%. Further analysis reveals that excessive crosslinking leads to excessive densification of the network structure, which, on the one hand, triggers stress concentration at microdefects, and, on the other hand, excessively restricts the motion of molecular segments, resulting in increased brittleness and compromised ductility. Experimental results demonstrate that a GA addition of 0.3wt% achieves the optimal balance between crosslinking density and network flexibility, achieving maximum tensile strength while maintaining a high strain at break.

[0070] Equilibrium swelling experiment:

[0071] Figure 7The swelling degree of GA-Cel / PAN membrane materials with glutaraldehyde mass fractions of 0.1-0.4wt% in pure water, pure ethyl acetate, and pure acetic acid was demonstrated. The study showed that the swelling degree of the cross-linked membrane material in pure water, pure ethyl acetate, and pure acetic acid decreased from 41%, 23%, and 3% to 31%, 18%, and 2%, respectively. As the GA mass fraction increased, the swelling degree of the membrane material in each component decreased. This is because GA, as a bifunctional cross-linking agent, forms a stable covalent bond structure with cellulose hydroxyl groups through aldehyde groups, constructing a three-dimensional cross-linked network between molecular chains. The introduction of GA enhances the interaction between cellulose chains, inhibits the phase separation process during membrane material formation, makes the overall structure of the membrane tend to be homogeneous and dense, reduces the free volume within the membrane, and hinders the penetration and dissolution of water, ethyl acetate, and acetic acid solvent molecules. By comparing the swelling degrees of membrane materials in pure water, pure acetic acid, and pure ethyl acetate, it was found that the swelling degree of water molecules in the membrane material was the largest. This is because water is a polar molecule, and cellulose contains a large number of hydroxyl groups, which are also strong polar groups; small-sized water has a higher diffusion efficiency in the cross-linked network. The combination of the above factors makes water molecules more easily dissolved in the cellulose membrane material.

[0072] Pervaporation performance test of GA-Cel / PAN membrane:

[0073] Figure 8 The effect of GA content on the acetic acid / water pervaporation separation performance of CA-Cel / PAN membrane material was studied. As GA increased from 0wt% to 0.4wt%, the separation factor of CA-Cel / PAN membrane material increased from 11 to 53, and the permeation flux decreased from 1951g·m-2·h-1 to 902g·m-2·h-1. PSI first increased and then decreased. From the above characterization analysis, it can be seen that with the addition of glutaraldehyde, the hydrogen bonds between the cellulose molecular chains formed a stable three-dimensional network structure through covalent bonding under the action of aldehyde groups, and the density of the membrane material increased. In addition, cross-linking led to an increase in the surface roughness of the membrane material, resulting in enhanced hydrophilicity and enhanced adsorption selectivity of the membrane material for water molecules. Overall, the separation factor of the membrane material increased, but the permeation flux decreased. Among them, the PSI was the largest when the cross-linking agent GA content was 0.3%. Therefore, the Cel-6(3) membrane material was used as a benchmark to further explore the effects of feed acid content and feed temperature operation on the pervaporation separation performance of the membrane material.

[0074] GA-Cel / PAN membrane acetic acid / water stability test:

[0075] The acid-water separation stability of GA-Cel / PAN membrane was tested at a feed temperature of 25°C and a water content of 10 wt%. Figure 9As shown, compared with the uncross-linked Cel / PAN membrane material, the total permeation flux and separation factor of the GA-Cel / PAN membrane material did not fluctuate significantly within 48 hours. Its permeation flux was stable at 1065 g·m-2·h-1 plus or minus 10%, and its separation factor was stable at 41 plus or minus 10%, indicating that the membrane has good stability. This excellent stability is attributed to the three-dimensional cross-linked network formed between the cellulose skeleton by GA molecules, which effectively inhibits the excessive swelling of the polymer chain segments in the acidic medium through covalent bonding, and at the same time enhances the membrane material's ability to resist the erosion of acetic acid molecules. Studies have confirmed that cross-linking modification not only enhances the separation selectivity of the membrane material for the acetic acid / water system, but also significantly improves its long-term operational stability in acidic materials, providing a more valuable membrane material solution for industrial separation processes in acidic environments.

[0076] The above-mentioned embodiments merely express several implementation methods of the present invention. Although the description thereof is relatively specific and detailed, it should not be understood as limiting the scope of the present invention.

Claims

1. A method for preparing a cellulose composite membrane based on phase separation-crosslinking modification, characterized in that: The method comprises the following steps: (1) dissolving cellulose in an ionic liquid and stirring the solution under heating conditions in a water bath to prepare a homogeneous membrane casting solution; (2) Add glutaraldehyde to the homogeneous casting solution and continue heating for 25-35 minutes; (3) Soaking the PAN nanofiber support layer in a NaOH solution on a hot plate for 25-35 min, then taking it out and repeatedly washing it with deionized water several times to remove residual NaOH to obtain a treated PAN support layer; (4) After the PAN support layer treated in step (3) is dried, it is spread flat on a smooth glass plate and fixed on a heating plate. The temperature is controlled to be 85-95°C. The casting liquid obtained in step (2) is poured along the edge of the PAN support layer. The distance between the scraper and the glass plate is controlled to be 220-280 μm. The film is scraped from bottom to top. Then, the glass plate is immersed in deionized water; after soaking, it is taken out and drained, and then dried to obtain the cellulose composite membrane.

2. The method according to claim 1, characterized in that In the step (1), the ionic liquid is AMIMCL, the water bath heating temperature is 90° C., the stirring time is 4 h, and the cellulose mass fraction of the prepared homogeneous casting solution is 6%.

3. The method according to claim 1, characterized in that The mass fraction of glutaraldehyde in step (2) is 0.1-0.4 wt%.

4. The method according to claim 1, wherein In step (3), the temperature of the heating plate is 65° C., and the concentration of the NaOH solution is 2 mol / L.

5. The method according to claim 1, wherein The drying in step (4) is specifically as follows: placing the PAN support layer in a vacuum oven and drying it at 90° C. for 1 hour.

6. The method according to claim 1, wherein In step (4), the glass plate is immersed in deionized water at room temperature for 24 hours.

7. The method according to claim 1, characterized in that The drying treatment in step (4) is specifically to place the product in a vacuum oven at 90° C. and dry it for 1 hour.

8. A cellulose composite membrane based on phase separation-crosslinking modification, characterized in that: The cellulose composite membrane based on phase separation-crosslinking modification is prepared by the method according to any one of claims 1 to 7.

9. Use of a cellulose composite membrane based on phase separation-crosslinking modification prepared by the method according to any one of claims 1 to 7, characterized in that: The cellulose composite membrane is used for separating mixed systems of ethyl acetate / water and acetic acid / water.

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